Telemetric system



Nov. 1, 1949 w. H. T. HOLDEN 2,486,784

TELEMETRIC SYSTEM Original Filed June 30, 1944 2 Sheets-Sheet l //vv/v TOR WA! ZHOL DEN AT TORNEY Nov; 1, 1949 w. H. 1'. HOLDEN TELEMETRIC SYSTEM 2 Sheets-Sheet 2 Original Filed June 50, 1944 /NV'NTOR my I HOLDEN AT TORNEV.

Patented Nov. 1, 1949 TELEMETRIC SYSTEM William H. T. Holden, Woodside. N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Continuation of application Serial No. 542,967, June 30, 1944. This application October 11, 1945, Serial No. 621,691

This invention relates to a telemetric system and more particularly to a telemetric system for controlling the flight recording apparatus of an aircraft trainer.

a In trainers heretofore employed to give training to an aircraft pilot simulating as closely as possible actual flight conditions, an instructors desk has been provided with controls operable by the instructor to introduce flight conditions which the trainee pilot must meet in his operation of the controls of the trainer. Also the instructors desk is provided with instruments which are operable from the trainer and from which instruments the instructor is able to check the flight reactions of the trainee to the flight conditions which the instructor has imposed.

Among these instruments is a flight recorder, sometimes called a crab because of its ability to move forwardly or sidewise in response to the operation ofthe controls of the trainer. This flight recorder is provided with one or more tractor wheels by which it may be propelled over a record sheet under the control of one or more driving motors at a speed proportional to the ground speed of the simulated flight being flown b the trainee. These tractor wheels may also be oriented to steer the flight recorder in accordance with the actual bearing of the simulated flight course. The recorder is also provided with a marking wheel which makes 2. record on the record sheet indicating the simulated flight course. A recorder of this type is disclosed in Patent 2,179,663 granted November 14, 1939, to E. A. Link, Jr.

It is the object of the present invention to provide a telemetric system for controlling a flight recorder which system is simple in construction and accurate and reliable in operation.

This object is attained in accordance with the present invention by the employment of electrically coupled generators and control transforminstrument corrected in accordance with the altitude and the temperature. In a trainer of the type disclosed in the application of R. C. Davis, E. J. Fogarty, and R. O. Rippere, Serial No. 542,986, filed June 30, 1944, the true air speed of the simulated flight is determined by a motor 4 Claims. (Cl. 318-18) control circuit which in turn is controlled from the motor control circuit which operates the indicated air speed instrument on the pilot's instrument panel and a duplicate instrument on the instructors desk and which is also controlled in accordance with the altitude at which the simulated flight is being flown. The bearing of the simulated flight, as determined by the steering control of the trainer, is determined by a motor control circuit which controls the setting of the compass on the pilot's instrument panel and of a duplicate compass which is located on the instructors desk.

Since these two motor control circuits determine the instantaneous values of the true air speed and the compass bearing of the simulated flight, they may be employed to also control the flight recorder. For this purpose a variable autotransformer is associated with the true air speed circuit and a generator having three Y connected stator windings is associated with the compass circuit. Potential from a source of alternating current is applied across the primary winding of the autotransformer and the potential derived from its secondary winding, which is varied by the movement of the brush of the variable autotransformer in accordance with the true air speed is applied across the single rotor winding of the generator. This rotor is rotatable by the compass motor circuit and causes the variation of the potentials induced into the three windings of the generator stator in a measure proportional to the rate of change of the compass bearing and causes a change of the strength of such potentials proportionally to the change in the true air speed.

Since the track of the simulated flight is determined not only by the air speed and flight bearing but also by the wind velocity and wind direction, provision is also made for introducing these factors into the control of the flight recorder. For this purpose a variable autotransformer and a second generator are provided at the instructor's desk. Potential from the same source of alternating current is applied across the primary winding of this autotransformer and the potential derived from its secondary winding, which is varied by the movement of the brush of the variable autotransformer by the instructor in accordance with the assumed velocity of the wind, is applied across the single rotor winding of this generator. This rotor is rotatable by the instructor to a position indicative of the direction of the wind and causes the variation of the potentials induced into the three windings of the generator stator in a measure proportional to the change of wind velocity and causes a change of the strength of such potentials proportionally to the change in the wind direction.

The stator windings of the two generators are linked together by transformer windings, whereby the potentials in the corresponding windings are added and applied to the corresponding windings of two control transformers of the same type. The stator windings of these transformers are connected in parallel and therotors are mounted upon the same shaft but with their windings disposed in quadrature. The potential induced into the rotor winding of the first of these transformers from the variation of the potentials applied to its stator windings is amplified and applied to the control phase winding of a two-phase servo-motor, the other winding of which is energized from the alternating current source. This servo-motor is geared by reduction gearing to the rotor shaft of the control transformers and when the servo-motor operates it rotates the rotor shaft until the rotor winding of the first transformer assumes an angular position corresponding to the sum of the angular positions of the rotors of the two generators or a position indicative of the direction of the true track of the simulated flight. At this time the rotor winding will be so positioned as to have no potential induced therein whereupon the servo-motor will cease its operation. The operation of the servo-motor is also effective to drive a generator which is coupled with a synchronous repeater on the flight recorder to orient the tractor wheels of the recorder whereby the flight recorder is steered in accordance with the true bearing of the simulated flight course.

At the time the rotor winding of the first control transformer was turned to the position in which it received no induced potential, the rotor winding of thesecond control transformer being mounted in quadrature with respect thereto, receives the maximum induced. potential from the stator windings associated therewith, which potential is proportional to the sum of the potentials imposed upon the rotors of the generators and corresponds to the true ground speed of the simulated flight. This potential is amplified and applied to the control phase winding of a second two-phase servo-motor, the other phase winding of which is energized from the alternating current source. This servo-motor is geared by reduction gearing to the shaft of a balancing autotransformer and drives the brush of such transformer to apply a potential of opposite phase to the input side of the associated amplifier circuit, until a value of such potential is attained which balances the input potential to such amplifier from the second rotor winding whereupon the operation of the servo-motor is arrested. The amount of rotation of the balancing transformer shaft is thus a measure of the ground speed and is employed to control the motors of the flight recorder which drive the tractor wheels thereof to progress the flight recorder over the record sheet at a speed commensurate with the ground speed of the simulated flight.

The invention having now been briefly described, reference may now be had to the following detailed description thereof taken in connection with the accompanying drawings, in which:

Fig. 1 discloses circuits embodying the present invention;

Fig. 2 is an isometric view of an interrupter away disclosing the steering and driving mechanism of a flight recorder.

Each of the autotransformers VI, V2 and V3 is provided with a fixed winding and an adjustable brush. The entire winding serves as a primary winding and that portion between one terminal and the point of engagement of the brush with the winding serves as a variable secondary winding. Brush BI of the transformer VI is mounted on the shaft I00 which is rotated to assume an angular position commensurate with the instant value of the true air speed of the simulated flight by the true air speed circuit of the trainer and the brush B2 of the transformer V2 is manually rotatable to assume an angular position commensurate with the assumed value of the wind velocity.

The generators GI, G2 and G3, the control transformers M4 and M5, and the synchronous repeater M6 are of the same type, each having a single rotor winding and three stator windings. While the stator windings are disclosed as Y-connected, it is to be understood that they could be A-connected. The rotor RI of generator GI is mounted on a shaft IOI which is rotated to assume an angular position commensurate with the instant value of the compass bearing of the trainer in its simulated flight and the rotor R2 of generator G2 is mounted on a shaft I02 which is manually rotated to assume an angular position commensurate with the assumed wind direction. The autotransformer VI and the generator GI are located in the apparatus cabinet associated with the trainer and the autotransformer V2 and the generator G2 are associated with the instructors desk and are adjustable by the instructor. The similar windings of the stators of generators GI' and G2 are linked through the windings of the repeating coils T3, T4 and T5 with corresponding windings of the stators of the control transformers M4 and M5 through the serially connected resistances DI, D2 and D3 and resistances SI, S2 and S3. The rotors R5 and R6 of these transformers are mounted on a common shaft I03 but with their windings mounted in quadrature with respect to each other.

Since a control transformer of this type does not follow the movement of the transmitter generator connected thereto, the servo-motor SMI of the two-phase squirrel cage armature type has its shaft I04 geared to the rotor shaft I03 of the control transformers M4 and M5 through the gear reduction box I05, preferably having a gear reduction of 600 to 1, so that the shaft I03 is rotated through one complete revolution in response to 600 revolutions of the shaft I04 of the servo-motor SMI. The rotor R3 of the generator G3 is mounted on the shaft I06 which is driven through reduction gear box I01 from the shaft I04 of the servo-motor. Preferably this gear ratio is such that the shaft I06 is rotated one complete revolution in response to 50 revolutions of the shaft I04. The stator windings of the generator G3 are connected to the corresponding stator windings of the synchronous repeater M8, the rotor R8 of which is mounted on a shaft I83. This repeater is mounted on the flight recorder disclosed in Fig. 5, the shaft I08 being mounted vertically therein and carrying on its upper end a pinion I09.

A second servo-motor SM2 of the two-phase squirrel cage armature type has its rotor shaft H connected through the gear reduction box I II with the shaft I I2. Preferably the gear ratio of the box III is such that the shaft H2 is rotated through one complete revolution in response to 600 revolutions of the rotor shaft H0. Connected to the shaft H2 is the brush B3 of the adjustable autotransformer V3 and the operating fingers I I3 and H4 of two limit switches LI and L2. These switches are provided to open the circuit through one phase winding of the servo-motor SM2 when it has rotated the brush B3 to a point adjacent to either end of the winding of transformer V3 to prevent the movement of the brush B3 off the winding. The shaft H2 also carries a pinion H5 for driving the interrupter apparatus of Fig. 2.

The interrupter apparatus of Fig. 2 comprises a frame II 6 in the forwardly extending arms H1 and H8 of which is .journaled a fluted shaft H9. The shaft H9 is rotatable at any desired slow speed by the synchronous motor M1, which is energized from a commercial source AC of 115 volts 60 cycle alternating current, through the reduction gear box I constituting a part of the motor and the spur gears I2I and I22. Slidable along the fluted shaft II9 but driven thereby is a drum I23 having a raised cam surface I24 of a substantiall V-shape, the base of which is disposed at the left end of the drum and is substantially as wide as the circumference of the drum and the apex of which is disposed adjacent to the right end of the drum.

The drum is embraced between the arms I25 and I26 which are slidable on the shaft H9 and in holes through which the shaft H9 is freely rotatable. The rear ends of such arms are secured to the rack I21 which is meshed with the pinion H5 secured to shaft 2. Supported in any suitable manner on the frame of the inter-. rupter is a set of contact springs and operating mechanism therefor. This set of springs is best disclosed in Fig. 3 and comprises a movable spring I 28 whose contact I29 is normally engaged with contact I30 of spring I3I and whose contact I32 is normally out of engagement with contact I33 of spring I34. For moving spring I28 it is provided with an inturned portion I35 which is engaged by a stud I36 of insulating material secured to the end of operating lever I31. The lever I31 is provided at its forward end with ear I38 between which a cam roller I39 is rotatably mounted and which is operable by the cam surface I24 of the drum I23. The other end of the lever I31 is pivoted between ears I40 of supporting member I4I. A backstop member I42 is also provided into which is threaded a first adjusting screw I43 for adjusting the position of spring I34 and into which is threaded a second adjustin screw I44 for adjusting the position of spring I35.

Through the rotation of the pinion H5 by the servo-motor SMZ, the rack I21 is moved toward the right or toward the left dependent upon the direction of rotation of the motor and thus slides the drum I 23 along the shaft H9. Due to the configuration of the cam surface I24 carried by the drum I23, when the drum is moved to its extreme right position, the rotation of the drum I23 will cause a long closure of the contacts of springs I23 and I34 during each revolution of the drum but when the drum approaches its extreme left position, the rotation of the drum I23 will cause a short closure of the contacts of springs I28 and I34 during each revolution.

Spring I28 is connectable to terminal I13 which in turn is connected in parallel over conductor I12 to the windings of the driving motors of the recorder, the spring I3I is connected to a source of direct current potential and the spring I34 is connected to the commercial source AC of a1- ternating current.

The recorder of Fig. 5 is, as previously stated, of the type fully disclosed in Patent 2,179,663, granted November 14, 1939, to E. A, Link, Jr. In general it comprises a casin triangular in shape having a bottom plate I5I. Suitably secured to the underside of the plate I5I is a self-synchroous motor M6, the shaft I08 of which extends upwardly through the plate and is provided at its upper end with a pinion I09. The pinion I09 meshes with three relatively large ears I52, I53 and I54 mounted upon the upper ends of shafts I55, I56 and I51, respectively, which are journaled in the base plate I5I. Th gear ratio between the pinion I09 and the gears I52, I53 and I54 is l to 12. Obviously, the rotation of the motor shaft I08 will result in simultaneous and like motions of the shaft I55, I56 and I51.

Each of the shafts I55 and I56 extends downwardly through the plate I5I and through a bushing such .as I58, in the lower end of which is located a ball bearing journal. The lower end of each of these shafts projects below the bushing and has secured thereto a bracket I59 to which is secured a motor I60 of the telechron clock type. The shaft of the motor is journaled in the bracket I59 and carries a pinion (not shown) which meshes with a gear connected to the tractor wheel I6I which is journaled on a stub shaft secured to the bracket I59.

Secured to the motor and insulated therefrom are two brushes (not shown) which are electrically connected to the terminals of the field coil I62 .of the motor and which brushes engage with slip rings I63 and I64 insulatedly supported on the bushing I58. By means of the brushes and slip rings, power may be transmitted to the motor while the motor and the tractor wheel I6I driven thereby may be oriented by the rotation of the shaft I55.

The slip rings associated with the propeller motors carried by the two shafts I55 and I56 are connected in parallel to conductors I65 and I66, conductor I65 extending to one of the contacts of switch I61 carried by the cover plate I68 of the recorder casing, the other contact of which is connected by a conductor I69 of the flexible cable I10 to a ground terminal I1 I, and conductor I66 extending by another conductor I12 of the flexible cable to a terminal I13 which is connected to the movable spring I28 of the interrupter contact set. The terminals of the stator and rotor windings of the repeater M6 are also connected by conductors of the same flexible cable to terminals indicated by the bracket I14 corresponding to terminals of the stator and rotor windings of the generator G3 of Fig. 1.

The shaft I51 also projects downwardly through the plate I5I and terminates in a bifurcation in which a marking wheel I15 is suitably journaled. The marking wheel is adapted to receive ink from an inking roller I16 pivotally mounted on the shaft I51 by the links I11. The

recorder is thus supported by the two tractor wheels IBI and the marking wheel I15, the progress of the recorder being determined by the operation of the motors I60 geared to the tractor wheels IBI and the direction in which the recorder proceeds being determined by the orientation of the tractor wheels IBI and the marking wheel I15.

The manner in which the recorder is operated will now be described. It will be asumed that the interrupter drum I23 is at the time positioned with respect to the contact set as shown in Fig. 2 and that the, switch I61 on the recorder has been operated to its closed position. As the motor M1 rotates the drum I23, the cam surface I24 on the drum disengages the contact I29 of spring I28 from the contact I30 of spring I3I and engages contact I32 of spring I28 with contact I33 of spring I34, whereby the circuits of motors I60 of the recorder are closed once during each revolution of the drum and, since with the drum positioned as shown, each closure of the circuits of motor I60 will last during approximately onehalf of the revolution of the drum, the recorder will, therefore, advance step by step in the direction controlled by the instant orientation of the tractor wheels I6I and marking wheel I15.

It will now be assumed that a change in the direction and velocity of the wind occurs and that the instructor therefore rotates the brush B2 of the autotransformer V2 until a setting is secured indicative of the changed wind velocity and that the instructor rotates the rotor R2 of the generator G2 until a setting is secured indicative of the changed wind direction. The movement of the brush B2 of the autotransformer V2 changes the transformation ratio thereof whereby potential applied from the source of alternating current AC over conductor I18 to the primary winding of transformer T2 is induced into the secondary windings of transformer T2, is modified by the autotransformer V2 and is applied across the winding of rotor R2 of the generator G2. The energization of the winding of rotor R2 causes potential to be induced into the stator windings of the generator G2 thereby causing current to flow through the right windings of transformers T3, T4 and T5. The rotation of the rotor R2 causes the variation of the potentials induced into the stator windings of the generator G2 and a variation of the potentials applied across the right windings of transformers T3, T4 and T5. I

It will also be assumed that in the operation of the trainer in response to the operation of its controls by the trainee the brush BI of the autotransformer VI is rotated to a degree indicative of a change in the true air speed at which the simulated flight is being conducted and that the rotor RI of the generator GI is rotated to a degree indicative of a change in the compass bearing of the simulated of the brush BI of the autotransformer VI changes the transformation ratio thereof whereby potential applied from the source of alternating current AC over conductor I18 to the primary winding of transformer TI, is induced into the secondary winding of transformer TI, is modified by the autotransformer VI and is applied across the Winding of rotor RI of the generator GI. Energization of the winding of rotor RI causes potentials to be induced into the stator windings of the generator GI thereby causing current to flow through the left windings of flight. The movement transformers T2, T4 and TB, through resistances DI, D2 and D3 and the stator windings of control transformer M4 and in parallel therewith through resistances SI, S2-and S3 and the stator windings of'the control transformer M8. The rotation of the rotor RI causes the variation of the potentials induced into the stator windings of the generator GI and a change in the current flowing through the left windings of transformers T3, T4 and TI and through the stator windings of control transformers MI and M5.

Through the action of the transformers T3, T4 and T5, the potentials applied to the right windings thereof are induced into the left windings thereof and added to the potentials applied through the left windings thereof from the generator GI so that the potentials applied across the stator windings of the control transformers M4- and M5 are the summation of the potentials applied across the corresponding stator windings of the generators GI and G2. The terminating impedance into which the generators work must be very high compared with that of the control transformers for accurary. Thus in response to the rotation of the rotors RI and R2 of the generators GI and G2, and the resulting variation of the stator winding potentials of such generators the potentials in the stator windings of the transformers M4 and M5 are caused to vary to a degree commensurate with the summation of the degree of variation of the stator winding potentials of the generators.

The energization of the stator windings of the control transformer M4 induces potential into the winding of rotor R4 which is applied across the winding of potentiometer PI and the potential derived therefrom is applied across the input side of the amplifier circuit AMPI. This amplifier circuit may be of the general type disclosed, for example, in Patent No. 1,654,075, granted December 27, 1927, to W. S. Gorton and comprises two voltage amplifier tubes VTI and VT2 connected in cascade, a dual triode tube VT3 one unit of which serves to invert a portion of the output of the other unit thereof, and two amplifier tubes W4 and VT5 connected in push-pull relationship between the output circuits of the tube VT3 and the primary windings of output transformer T6. Filament heating current is supplied to the tubes of amplifier AMPI from the lower secondary winding of power transformer T1, the primary winding of which is connected over conductor I18 to the source of alternating current AC. Plate potential for the amplifier tubes VT4 and VT! is supplied from the upper secondary winding of transformer T1 through the rectifier tube VTB and screen grid potential is supplied to the tubes VT4 and VT5 from the upper secondary winding of transformer T1 through the rectifier tube VT6 and the potentiometerP3. The filaments of the rectifier tube VT6 are heated by current supplied through the middle secondary winding of transformer T1. Plate potential for tubes VTI, VT2 and VT3 is supplied from the plate battery BTi.

The potential applied from the winding of rotor R4 to the input side of the amplifier circuit AMPI is thus amplified and the amplified output potential is applied from the secondary winding of the output transformer T6 across one phase winding of the stator of servo-motor SMI. The other phase winding of this motor is energized from the source of alternating current AC applied thereto over conductor I18 and the w ings of tranformer T8. 50 long as there is an outacaavu 9 put potential from the amplifier circuit AMPI, both phase windings of the motor SMI will be energized and the motor will operate rotating the armature shaft I04 in one direction or the other dependent upon the polarity of the potential received from the winding of rotor R5, amplified by the amplifier AMP2, and impressed upon the control phase winding of the motor SMI, with respect to the instant polarity of the potential applied from the transformer T8 to the other phase winding. This polarity difference will in turn be dependent upon whether the summation of the movements of the rotors of the generators GI and G2 is in one or the other sense. The rotation of the armature shaft I04 results in the rotation of shaft I03 upon which the rotors R4 and R5 of the control transformers M4 and M5 are mounted at a slow speed as determined by the reduction gear box I05. As the rotor R4 is thus turned, the potential induced into its winding from the stator windings of the control transformer M4 is gradually reduced, the output potential from the amplifier circuit AMPI is gradually reduced and consequently'the speed of rotation of the servo-motor SMI is reduced until the rotor R4 assumes a position in which the potential in- .duced into its winding becomes zero at which time the control phase winding of motor SMI receives no potential and motor SMI comes to rest.

The rotation of the shaft I04 of motor .SMI in addition to rotating the rotors of control transformers M4 and M5 as just described, also rotates the shaft I06 of the rotor R3 of the generator G3 through the interposed reduction gear box I01 and, since the winding of rotor R3 is energized by current from the source AC applied thereto through the windings of transformer T8, the rotation of the rotor winding establishes varying potentials in the stator windings of generator G3 and a corresponding potential variation in the stator windings of the synchronous repeater MS of the flight recorder of Fig. 5. As the winding of the rotor R6 of the repeater M6 is also energizedin parallel with the rotor winding'of the generator M3, the rotor R6 rotates in synchronism with the rotor R3 and through the pinion I09 mounted on the shaft I08 of rotor R6 and the spur gears I52, I53 and I54 rotate the shafts I55, I56 and I51 to orient the tractor wheels I6I and the marking wheels I15 of the flight recorder. Since it has been assumed that the reduction gear box I01 has a reduction gear ratioof 60 to 1 and the pinion gear I09 and spur gears I52, I53 and I54 of the flight recorder have a gear reduction ratio of 12 to 1, the shafts I55, I56 and I51 are oriented one complete revolution in response to 600 revolutions of the rotor shaft I04 of the motor SMI. The motor SMI thus serves to change the orientation of the flight recorder in accordance with the change in the bearing of the simulated flight.

At the time the rotor R4 of the control transformer M4 is rotating to a position in which the potential induced into its winding is reduced to zero, the rotor R5 of control transformer M5 being mounted on the common shaft I03 in quadrature to the rotor R4 receives an increasing induced potential from its associated stator windings. This potential is applied across the winding of potentiometer P2 and the potential derived therefrom is applied across the input side of the amplifier circuit AMP2. This amplifier circuit is idential with the amplifier circuit AMPI and is similarly supplied with filament heating current from the power transformer T1 and with plate and screen grid potentials from the rectifier tube VT! and the associated potentiometer P3.

The output potential from the amplifier circuit AMP! is applied through the output transformer T9 to the control phase stator winding of the servo-motor 8M2, the other phase winding of which is supplied with potential from the source AC over windings of transformer T9 and over the normally closed contacts of the limit switches L2 and LI. The motor SM2 therefore operates rotating its rotor shaft H0 and through the reduction gear box I I I rotating the shaft H2.

The motor 8M2 will rotate in one direction or the other dependent upon the polarity of the potential received by the winding of rotor R5, amplified by the amplifier AMP2 and impressed upon the control phase winding of the motor 8M2, with respect to the instant polarity of the potential applied from the transformer T8 to the other phase winding, and this polarity difference will in turn be dependent upon whether the summation of the movement of the brushes BI and B2 of the autotransformers VI and V2 is in one or the other sense.

As the shaft II2 rotates it moves the brush B3 of the autotransformer V3, the winding of which is energized by potential applied thereto from the source AC over conductor I18 and the windings of transformer TIO. This potential, because of the association of resistance I19 and condenser I00 with the secondary windings of transformer TIO, is displaced degrees in phase with respect to the phase of the potential impressed from the windin of rotor R5 upon the input side of the amplifier circuit AMPZ and consequently the potential derived from the autotransformer V3 through the adjustment of its brush B3 by the motor SM2 being also applied to the input side of the amplifier circuit, tends to gradually balance the potential applied from the winding of rotor R5 and to cause the speed of motor SM2 to become gradually reduced until the rotor R5 comes to rest, at which time the potential induced into its winding and applied to the input side of the amplifier circuit AMP2 will be completely balanced by the potential applied through the autotransformer V3. No potential will therefore be effective in the input side of the amplifier circuit and consequently no potential will be impressed from the output transformer T9 upon the control phase stator winding of the motor 8M2. Motor SM2 will therefore be brought to rest.

The potential induced into the Winding of rotor R5 being a summation of the potentials impressed upon the windings of the rotors RI and R2 of generators GI and G2 incident to changes in the true air speed of the simulated flight and in the wind velocity, the amount of rotation of shaft II2 by the motor SM2 under the control of the rotor R5 is a measure of the change in the actual ground speed of the simulated flight.

The rotation of shaft II2 also rotates the pinion II5 carried thereby and the pinion meshing with rack I21 of the interrupter causes the movement of the drum I23 along the shaft I I9 in the manner previously described. If it be assumed that the combined effect of the change in the true air speed and the change in the wind velocity has been to rotate the shaft H2 in a. direction indicative of an increase in the ground speed of the simulated flight, the pinion II5 will cause the drum I23 to be moved toward the right with respect to the interrupter contact set thereby increasing the length of the closure between springs I 28 and I34 during each revolution of the drum I23 and thereby increasing the length of the interval during which the circuits of the propelling motors I60 of the flight recorder are closed during each unit period of time. Thus the flight recorder is advanced by longer steps indicative of an increased ground speed of the simulated flight.

Had the shaft H2 been rotated in the opposite direction indicative of a reduced ground speed then the drum I23 would have been moved toward the left with respect to the interrupter contact set thereby reducing the length of the closure between springs I28 and I34 during each revolution of the drum I23 and thereby reducing the length of the intervals during which the circuits of the propelling motors I60 of the flight recorder are closed during each unit period of time.

It is to be noted that between successive c10- sures of the circuits of the propelling motors I60 of the flight recorder, contacts I28 and I3I of the interrupter contact set are closed thereby connecting the field windings of the motors in series with the source BT3 of direct current. The connection of direct current to the motors locks them against operation so that between propelling impulses the flight recorder is held against accidental displacement.

If the shaft H2 should be driven by the motor 8M2 until the brush B3 carried thereby approaches one or the other end of the winding of the autotransformer V3, one or the other of the fingers H3 and H4 carried by the shaft will operate the contacts LI or L2 of the limit switches to open the circuit of one phase winding of the motor SM2 to arrest further rotation of the motor and to thus prevent the brush B3 from being driven out of engagement with the winding of the autotransformer.

While the generators GI and G2 and the control transformers M4 and M5 have been illustrated and described as having three-winding stators, it is to be understood that generators and transformers having two-winding stators could be employed.

This application is a continuation of application Serial No. 542,967, filed June 30, 1944 for a Telemetric system.

What is claimed is:

1. In a telemetric system a plurality of transmitters each having a multiwinding stator and a rotor, means for applying potentials to said rotors proportional to the magnitudes of difierent forces, means for rotationally displacing said ro tors proportionally to the directions of said respective forces, two receivers each having a multiwinding stator connected to the stators of said transmitters and a rotor, a motor geared to the rotors of said receivers-and a thermionic amplifier circuit interposed between the rotor of one of said receivers and said motor for controlling said motor to bring the rotor of said one receiver into a rotational position corresponding to the vectorial sum of the positions of the rotors of said transmitters and to bring the rotor of said other receiver into a rotational position in which the potential impressed therein is proportional to the vectorial sum of the potentials applied to the rotors of said transmitters.

2. In a telemetric system, a plurality of transmitters each having a multiwinding stator and a rotor, means for applying potentials to said rotors proportional to the magnitudes of different forces, means for rotationally displacing said rotors proportionally .to the directions of said respective forces, two receivers each having a multiwinding stator and a rotor, transformers for linking the corresponding stator windings of said transmitters and said receivers together, a motor geared to the rotors of said receivers and a thermionic amplifier circuit interposed between the rotor of one of said receivers and said motor for controlling said motor to bring the rotor of said one receiver into a rotational position corresponding to the vectorial sum of the positions of the rotors of said transmitters and to bring the rotor of said other receiver into a rotational position in which the potential induced therein is proportional to the vectorial sum of the potentials applied to the rotors of said transmitters.

3. In a telemetric system, a plurality of transmitters each having a multiwinding stator and a rotor, means for applying potentials to said rotors proportional to the magnitudes of difierent forces, means for rotationally displacing said rotors proportionally to the directions of said respective forces, two receivers each having a multiwinding stator connected to the stators of said transmitters and a rotor, a first motor geared to the rotors of said receivers, a thermionic amplifier interposed between the rotor of one of said receivers and said motor for controlling said motor to bring the rotor 01 said one receiver into a rotational position corresponding to the vectorial sum of the positions of the rotors of said transmitters and to bring the rotor of said other receiver into a rotational position in which the potential induced therein is proportional to the vectorial sum of the potentials applied to the rotors of said transmitters, a second motor, a thermionic amplifier circuit interposed between the rotor of said other receiver and said second motor whereby said motor is driven at a speed proportional to the potential impressed from said rotor upon said amplifier circuit and means controlled by said second motor for applying an opposing potential to the input of said latter amplifier circuit until the potential applied to said amplifier circuit from said rotor becomes balanced whereupon said second motor ceases to operate.

4. In a telemetric system, a plurality of transmitters each having a multiwinding stator and a rotor, means for applying potentials to said rotors proportional to the magnitudes of different forces, means for rotationally displacing said rotors proportionally to the directions of said respective forces, two receivers each having a multiwinding stator connected to the stators of said transmitters and a rotor, a first motor geared to the rotors of said receivers, a thermionic amplifier interposed between the rotor of one of said receivers and said motor for controlling said motor to bring the rotors of said one receiver into a rotational position corresponding to the vectorial sum of the positions of the rotors of said transmitters and to bring the rotor of said other receiver into a rotational position in which the potential induced therein is proportional to the vectorial sum of the potentials applied to the rotors of said transmitters, a second motor, a second thermionic amplifier circuit interposed between the rotor of said other receiver and said second motor whereby said latter motor is driven at a speed proportional to the potential impressed from said rotor upon said second amplifier circuit and a variable autotransformer operable 13 by said second motor for applying an opposing potential to the input of said amplifier circuit until the potential applied to said amplifier circult, from said rotor becomes balanced whereupon said second motor ceases to operate. 5

WILLIAM H. 'r. HOLDEN.

REFERENCES CITED The following references are of record in the 10 file of this patent:

Number 14 UNITED STATES PATENTS Name Date Behr July 26, 1938 Mac Laren Apr. 11, 1939 Koster July 4, 1939 Link Nov. 14, 1939 Norden Oct. 26, 1943 Stout Aug. 15, 1944 Lowkrantz Oct. 10, 1944 Dehmel Jan. 2, 1945 Gumley Feb. 26. 1946 

